X5 braking issue

[Greeny]

Had the front brakes lock on the car today, all the brake warning lights came on, by the time I pulled, slowly, into somewhere safe, disks were smoking hot!
While waiting for the AA, lights went off and the brakes freed off, and l carefully drove home with the AA man following me. Brakes did not seize on again, but the pedal does not seem right, fine if you stamp on them, but if you push slowly, pedal goes really long, but brakes still work.
Reservoir full, one brake pipe replaced recently.
Any ideas?

[motorhole]

Pedal might feel long now if the experience had boiled the brake fluid. Likely if the discs/pads were smoking when you came to a stop and it took some time for them to free off. Get a fluid change and should be good again. As for the cause of the issue I couldn't say...somebody with more experience of X5s or modern BMWs may have more constructive suggestions.

[Ozzie Osmond]

^^^^ Probably caused by a seized calliper. But if it was both sides at once maybe a valve somewhere - but very, very unusual.

[Greeny]

All fluid replaced, and system bled, still the same.
Guy on X Drivers says the ABS modulator also has to be bled, will suggest this on Monday to the garage.

[Megaflow]

A seized brake caliper wouldn't bring on brake warning lights, unless it seizes to the point of locking a wheel, but a seized caliper is going to struggle to do that.

Did one front lock or both?

If it's one I'd suggest a dodgy ABS unit, this would probably also explain the soft pedal.

[imagineifyeswill]

In the past year Ive had trouble with 2 vehicles with the brakes sticking on solid, a Fiat Scudo and a VX Vectra both caused by internal faults in the servo, in the case of the Fiat apparently quite common. Is the vehicle Diesel, you say brakes are fine if you hit the hard but long pedal travel when applied slowly, servo assistance on diesel vehicles is by vacum pump and its perfectly normal for the pedal too have a long travel on soft application, most will go almost to the floor.

[Ozzie Osmond]

Brings us back to valves - either in the servo or the ABS unit. Both very unusual so I'd be suspecting the level of competence with which previous brake work was carried out.

[Greeny]

New Master Cylinder fitted, problem solved!